The invention relates to a quick-change chuck, especially for a locking sleeve receiving a tool.
More especially the chuck is adapted to be fitted on a shank sleeve fitted or fittable on the machine tool, into which sleeve the locking sleeve can be inserted to rotate therewith. A locking nut screws on to the forward end of the locking sleeve, and a ball sleeve is carried by the shank sleeve and connectable with the sleeve. The ball sleeve has at its distal end an annular extension piece with locking balls held radially movably therein which can engage radially in an annular groove of the locking nut which is provided internally with inclined flanks on both sides of the locking balls. The annular extension piece with one end forms an axial stop against which the locking nut can abut with an abutment face thereon. The annular extension piece and/or the locking nut can bear each with an annular face axially against the free annular end face of the shank sleeve. A connector bush or control sleeve is axially displaceably held on the ball sleeve and is subject to the axial pressure of a spring supported against the ball sleeve, which connector bush has on the end section axially adjacent to the locking balls an inner reception part and a substantially frusto-conically converging ramp face by means of which the locking balls engage, on axial displacement of the connector bush into its locking position radially into the annular groove of the locking nut. In the case of contrary axial displacement of the connector bush into its release position the locking balls emerge radially from the annular groove liberating the locking nut with locking sleeve, and can enter the receiving part of the connector bush.
A quick-change chuck of this kind is known (Ger. Pat. Sp. No. 12 99 488).
For the insertion of a locking sleeve and for its coupling the connector bush must be drawn by hand into the release position, that is axially downwards in operation, and held in this release position against spring force during the insertion of the locking sleeve. After the insertion the connector bush can be released and then by spring force is pushed back of its own accord into its locking position, with consequent pressing of the locking balls radially into the annular groove of the locking nut. This requires both hands, namely the left hand which draws the connector bush into the release position and holds it, and the right hand which inserts the locking sleeve. This operation is quite demanding. Thus there is a limit to the reduction of the fitting and changing times. Sometimes this operation is also especially irksome, for example in the case of multi-spindle drill heads with narrow spindle intervals and poorly accessible spindles. Then sometimes little space is available for actuating the connector bush with one hand and holding and inserting the locking sleeve, or holding and withdrawing it in the case of release, with the other hand.